Actuator for the actuation of at least one movable member, in particular for changing gear ratios in a motor vehicle transmission

ABSTRACT

An actuator for the actuation of at least one movable member of a motor vehicle transmission. The actuator includes a housing, at least one electric motor having a stator and a rotor mounted on a rotor shaft extending along an axis X 1 , a motor pinion fixed to the opposite end of the shaft from the rotor, a circuit board for supplying power to the stator and controlling the electric motor, and a reduction mechanism driven by the motor pinion. The housing defines a first volume in which the electric motor and the circuit board are received. The circuit board is located axially along the axis X 1  between the electric motor and the motor pinion. The actuator further includes a cover defining a second volume in which the reduction mechanism is received, the housing and the cover each have guides for guiding the reduction mechanism.

The invention relates to an actuator for the actuation of at least onemovable member. It is applicable in particular in the field of actuatorsfor motor vehicle transmissions. However, numerous other applicationsare possible.

More specifically, the invention relates to an actuator for changinggear ratios in a motor vehicle transmission or gearbox. Such an actuatorfinds use in a hybrid transmission of a motor vehicle, having for theone part a driving combustion engine and for the other part an electricmachine.

There is a need to change the gear ratios of the transmission in orderthat the combustion engine and/or the electric machine operate in theiroptimum range of use. The actuator according to the invention performsthis function.

An actuator for changing gear ratios in a gearbox comprising an electricmotor and a fork spindle which is moved axially to engage or disengage agear ratio of the gearbox is known from document WO2018/146393A1. Thisactuator has step-down means for demultiplying rotational movementbetween the output shaft of the electric motor and a pin which is offsetwith respect to the axis of rotation of the electric motor, the pinbeing engaged in an oblong opening in a claw system so as to bring aboutthe axial movement of the fork spindle in linear travel along theopening under the action of the electric motor.

This solution has the drawback of providing a bulky step-down means,this going against the objectives of the automotive industry aiming toreduce the weight and size of components. Moreover, the aforementioneddocument does not provide any means for controlling the electric motor.

Document WO2020/065088A1 discloses an actuator for the actuation of amovable flap. This actuator is composed of a housing which receives anelectric motor and a circuit board, of an intermediate plate and of acover. The use of such an intermediate plate makes the actuator complexto manufacture. This actuator is not optimized in terms of weight andcompactness.

The subject of the present invention is to improve the currentsolutions, in particular by providing a solution having the aim ofmaking such an actuator for changing gear ratios of a motor vehicletransmission as compact as possible whilst still integrating a means forcontrolling the electric motor.

The term “transmission” is synonymous with a gearbox of a motor vehicle.

More particularly, the invention relates to an actuator for theactuation of at least one movable member of a motor vehicletransmission, said actuator comprising a housing, at least one electricmotor having a stator and a rotor mounted on a rotor shaft extendingalong an axis X1, a motor pinion fixed to the opposite end of the shaftfrom the rotor, a circuit board for supplying power to the stator andcontrolling the electric motor, a reduction mechanism driven by themotor pinion, said housing defining a first volume in which the electricmotor and the circuit board are received, the circuit board is locatedaxially along the axis X1 between the electric motor and the motorpinion, the actuator moreover comprises a cover defining a second volumein which the reduction mechanism is received, the housing and the covereach have guide means for guiding the reduction mechanism.

Therefore, an actuator according to the invention will be able to solvethe problems set out above. In particular, positioning the circuit boardbetween the electric motor and the motor pinion makes it possible tointegrate the power and control electronics into an actuator in acompact way.

According to the invention, the housing has at least one guide means forguiding the reduction mechanism also serving as means for centring thecircuit board in the housing.

According to the invention, the circuit board has at least one openingof closed contour through which the shaft of the electric motor passes.The shaft of the electric motor passes through this opening on eitherside. The circuit board also has at least one opening of closed contourthrough which the guide means passes. In a particularly advantageousway, the circuit board bears against a shoulder of the guide means.

According to one feature of the invention, the outer contour of thecircuit board substantially closely follows the inner contour of thehousing and the circuit board is fixed to the housing by way of fixingmeans, in particular screws.

Preferentially, a holding plate is arranged so as to hold the electricmotor in the housing and the holding plate is fixed to the housing byway of fixing means, in particular screws.

As an alternative, the circuit board may be fixed to the cover by way offixing means, in particular screws.

According to another feature of the invention, the housing comprises aperipheral groove in which a seal is disposed in order to ensureleaktightness between the housing and the cover.

Preferentially, the actuator is able to be fixed directly on thetransmission of the vehicle and the outer surface of the cover has agroove in which a seal is positioned in order to ensure leaktightnessbetween the transmission and the cover.

Advantageously, the actuator comprises at least one pin that is able tobe engaged in a movable member of the transmission. The pin is locatedon the outside of the cover and as a result on the outside of theactuator. The pin may have a shape which interacts with the movablemember, for example a conical shape or as a variant, a spherical shape.

The pin is able to be engaged in an opening, for example an oblongopening, so as to bring about the axial movement of a fork in lineartravel along the opening under the action of the electric motor. The pinis able to travel in the opening around a neutral central position andtwo end positions.

According to the invention, the reduction mechanism is locatedkinematically between the motor pinion and the pin. The reductionmechanism comprises at least one gear wheel mounted on at least oneshaft. More specifically, the reduction mechanism comprises astepped-pinion wheel and a toothed-sector pinion.

According to the invention, the stepped-pinion wheel and thetoothed-sector pinion each extend in a plane orthogonal to the axis X1.This reduction mechanism architecture makes it possible to obtain anespecially compact actuator.

More specifically, the stepped-pinion wheel comprises a first pinion anda second pinion, the first pinion is coupled to the motor pinion and thesecond pinion is coupled to the toothed-sector pinion, thestepped-pinion wheel is mounted on a shaft extending along an axis X2offset radially with respect to the axis X1 of the shaft of the electricmotor. Preferably, the stepped-pinion wheel is in one piece, the firstpinion and the second pinion are coaxial.

According to the invention, the toothed sector of the pinion extends inan angular range of between 90° and 180°, preferably between 100° and120°. As a variant, the toothed sector of the pinion may extend to 360°.The toothed-sector pinion is mounted on a shaft extending along an axisX3 offset radially with respect to the axes X1 and X2.

According to an additional feature of the invention, the pin is mountedoffset along an axis X4 at one end of the shaft of the toothed-sectorpinion by way of a connecting rod.

According to the invention, the axes X1, X2, X3 and X4 are parallel.

According to one feature of the invention, the actuator is configured tochange gear ratios of a motor vehicle transmission, in particular ahybrid transmission.

Advantageously, the actuator according to the invention comprises threeelectric motors, each electric motor being associated with its ownreduction mechanism and its own pin. In this way, the actuator is ableto control the changing of six transmission ratios. This is because eachelectric motor, via its own reduction mechanism, is able to move theassociated pin into two end positions, each corresponding to onetransmission ratio. In other words, each electric motor, via its ownreduction mechanism and its associated pin, is able to control two gearratios of the transmission of the vehicle. The electric actuatoraccording to the invention with its three electric motors isadvantageous in transmissions with six gear ratios.

For example, in the context of the hybrid transmission disclosed indocuments WO2015/197927A1 and WO2019/219294A1, the first electric motorof the actuator according to the invention may be linked to two gearratios associated with the electric machine whereas the second electricmotor of the actuator according to the invention may be linked to twogear ratios of the combustion engine, for example gear ratios 1 and 3,and the third electric motor of the actuator according to the inventionmay be linked to two other gear ratios of the combustion engine, forexample gear ratios 2 and 4.

Other features and advantages of the invention will become apparent uponreading the following text of exemplary embodiments explained in detail,with reference to the appended Figures.

FIG. 1 shows a bottom view of the actuator according to the invention;

FIG. 2 shows a top view of the actuator according to the invention;

FIG. 3 shows a perspective and partially sectional view of the actuatoraccording to the invention;

FIG. 4 shows a perspective and sectional view of the actuator accordingto the invention;

FIG. 5 a and FIG. 5 b respectively show a perspective view and asectional view of a guide means for guiding a shaft of the reductionmechanism;

FIG. 6 shows a perspective view of the contact between the circuit boardand the housing;

FIG. 7 shows a cutaway perspective view of a holding plate for anelectric motor;

FIG. 8 shows a sectional view of a guide means for guiding a shaft ofthe reduction mechanism;

FIG. 9 a and FIG. 9 b respectively show a perspective view and asectional view of an electric connector of the actuator according to theinvention;

FIG. 10 shows a sectional view of the electric actuator according to theinvention fixed on a gearbox of a motor vehicle;

FIG. 11 shows an alternative embodiment of the invention;

FIG. 12 and FIG. 13 show a variant embodiment of the actuator accordingto the invention;

FIG. 14 and FIG. 15 show another variant embodiment of the actuatoraccording to the invention.

FIG. 1 shows an actuator 10 according to the invention. The actuator 10is formed by two main parts, specifically a housing 20 and a cover 30 inwhich multiple elements are received. The focus of this FIG. 1 is thehousing 20 of the actuator 10. The housing 20 is made of metal, such asaluminium or an aluminium alloy, for example. As a variant, the housing20 may be made of an injection-mouldable plastics material. The functionof the housing 20 is to accommodate the electric motors 1 in thededicated recesses 21. The housing 20 thus forms a housing common to theelectric motors 1.

In a first embodiment of the invention, three electric motors 1 arereceived in three respective recesses 21. The recesses 21 of theelectric motors 1 are produced with a complementary shape to the shapeof the electric motors. Reinforcements 22 in the form of ribs areprovided between each recess 21 to stiffen the housing 20.

The housing 20 also incorporates an electric connector 27 in order tosupply power to the electric motors 1 and all of the electric componentsnecessary for the operation of the actuator 10.

The housing 20 is joined to the cover 30 by way of fixing screws 23located on the periphery of the housing 20 and of the cover 30.

The cover 30 of the actuator 10 can be seen in FIG. 2 . The cover 30 ismade of metal, such as aluminium or an alloy, for example. As a variant,the cover 30 may be made of an injection-mouldable plastics material. Inthe case of the present invention, the housing 20 and the cover 30 aremade of die-cast aluminium. The housing 20 or the cover 30 mayaccommodate a cooling circuit if the surrounding temperatures areexcessively high.

The actuator 10 is able to be fixed directly on the transmission of thevehicle, such as the gearbox, for example, by way of fixing means 31, inparticular openings in which screws are placed. The outer surface of thecover 30 has a groove 33 in which a seal 34 is positioned in order toensure leaktightness between the transmission and the cover 30. Theelements situated inside the closed contour of the seal 34 are in directcontact with the transmission of the vehicle. In the present case, threepins 8 are each able to be engaged in a movable member of thetransmission, linked for example to a fork and/or a claw. The pins 8 aretherefore located on the outside of the cover 30. The pins 8 have ashape which interacts with their respective movable member, for examplea conical shape.

Each pin 8 is able to be engaged in an opening, for example an oblongopening, in a claw so as to bring about the axial movement of a fork inlinear travel along the opening under the action of the electric motor.The pin is able to travel in the opening around a neutral centralposition and two end positions. This actuation kinematics is describedin the published document WO2018/146393A1.

FIG. 3 shows the interior of the actuator 10 according to the invention.Although FIG. 3 is a perspective and partially sectional view focused ona single electric motor 1 and its associated kinematics as far as thepin 8, the three electric motors 1 and the actuation kinematics of thepins 8 are all independent but identical in the actuator 10.

The housing 20 and its recess 21 in which the electric motors 1 arereceived can therefore be seen in FIG. 3 . In order to hold the electricmotors 1 fixedly in the housing 20, holding plates 6 are used so as topress the electric motors 1 against the base of their respective recess21.

The electric motors 1 are DC electric motors and are each constituted bya stator 2 and a rotor 3 mounted on a rotor shaft 4 extending along anaxis X1. A motor pinion 5 is fixed to the end of each shaft on theopposite side from the rotor 3 and makes it possible to drive areduction mechanism 40 formed by the gear wheels 41, 42, 46 that aremounted on the shafts 44, 45.

The reduction mechanism 40 is located kinematically between the motorpinion 5 and the pin 8 and comprises a stepped-pinion wheel 43 and atoothed-sector pinion 46.

The stepped-pinion wheel 43 comprises a first pinion 41 and a secondpinion 42, the first pinion 41 is coupled to the motor pinion 5 and thesecond pinion 42 is coupled to the toothed-sector pinion 46, thestepped-pinion wheel 43 is mounted on the shaft 44 extending along anaxis X2 and is offset radially with respect to the axis X1 of the shaft4 of the electric motor 1. The first pinion 41 has a larger diameterthan the second pinion 42. The gear wheels 41, 42, 46 are overmoulded onthe shafts 44, 45. The gear wheels 41, 42, 46 are for example made ofpolyphthalamide reinforced with glass fibres (PPA), having very highstiffness and strength and also resistance to high temperatures and tochemicals. As a variant, the gear wheels may be made of polyamidereinforced with glass fibres (PA).

The stepped-pinion wheel 41, 42, 43 and the toothed-sector pinion 46each extend in a plane orthogonal to the axis X1.

The toothed sector of the pinion 46 extends in an angular range ofbetween 90° and 180°, preferably between 100° and 120°. Thetoothed-sector pinion 46 is mounted on the shaft 45 extending along anaxis X3 offset radially with respect to the axes X1 and X2. The pin 8 ismounted offset along an axis X4 at one end of the shaft 45 of thetoothed-sector pinion 46 by way of a connecting rod 9. This connectingrod 9 is also located on the outside of the cover 30. The axes X1, X2,X3 and X4 are parallel.

A circuit board 11 serving to supply power to the stator 2 and tocontrol each electric motor 1 is located axially along the axis X1between each electric motor 1 and each motor pinion 5. The housing 20defines a first volume in which the electric motors 1 and the circuitboard 11 are received, thus forming an electronic sub-assembly.

The circuit board 11 is fixed to the housing 20 by way of fixing means13, in particular screws. The outer contour of the circuit board 11substantially closely follows the inner contour of the housing 20. Thecircuit board 11 has three openings 12 of closed contour, through eachof which passes the rotor shaft 4 of each electric motor 1.

The circuit board 11 makes it possible to manage the power electronics,the control electronics and the self-diagnosis function. Consequently,all of the functions (detection of the position of the pins 8 forclosed-loop control, electric power supply and connection to the bus ofthe vehicle) can be found on the circuit board. Therefore, the circuitboard 11 incorporates all of the electronic components necessary for theoperation of the electric actuator, such as rotation sensors 56 facingthe shafts 45, for example, in order to determine the position of thepins 8. Moreover, the electric power supply for the motors 1 is close tothe electric connector 27. The circuit board 11 is connected to theelectric motors 1 by crimp or solder contacts.

The reduction mechanism 40 is received in the cover 30 which defines asecond volume. The housing 20 and the cover 30 each have guide means 24,32 for guiding the shafts 44, 45 of the reduction mechanism 40.

The housing 20 comprises a peripheral groove 25 in which a seal 26 isdisposed in order to ensure leaktightness between the housing 20 and thecover 30.

FIG. 4 makes it possible to better depict the kinematics between theelectric motor 1, the reduction mechanism 40 and the pin 8.

The housing 20 has a guide means 24 in the form of a blind holeaccommodating one end of the shaft 44 of the stepped-pinion wheel 43.The cover 30 also has a guide means 28 in the form of a blind holeaccommodating the other end of the shaft 44 of the stepped-pinion wheel43.

The cover 30 also comprises a through-hole 32 for the passage andguidance of the shaft 45 of the toothed-sector pinion 46.

On its end facing the circuit board 11, the shaft 45 comprises a magnet35 for detecting the position of the pin 8 by virtue of a sensor 56fixed on the circuit board 11. The sensor 56 is preferably a Hall effectsensor.

FIGS. 5 a and 5 b respectively show a perspective view and a sectionalview of the guide means 24, in which the shaft 44 of the reductionmechanism 40 is received. The guide means has an axial slot 47 forfacilitating the insertion of the shaft 44. This axial slot 47 makes itpossible to drive out the air whilst still preventing the formation ofan air pocket when the shaft 44 is being inserted into the guide means24. The guide means 28 may also have such an axial slot. The circuitboard has an opening 50 of closed contour through which the guide means24 passes. The guide means 24 has a shoulder 55 against which thecircuit board bears. The guide means 24 serves both to guide thereduction mechanism in rotation and also as a means for centring thecircuit board 11 in the housing 20.

FIG. 6 shows the circuit board 11 in contact with pins 37 of the housing20 in order to dissipate the heat generated by the circuit board 11.Thermal paste 38 is positioned between the pins 37 and the circuit board11 in order to improve the transfer of heat energy from the circuitboard 11 to the housing 20 which, by virtue of its material, dissipatesthe heat. A channel 39 is provided on the periphery of the pins 37 inorder to recover the excess thermal paste 38.

FIG. 7 shows the positioning of one of the electric motors 1 and itbeing held in position in its dedicated recess 21. During operation, theelectric motor 1 is subject to acceleration and inertia, which meansthat it is necessary to correctly position and hold it in its recess 21.The electric motor 1 must also be correctly oriented to allow conductionvia the terminals B+, B− with the circuit board 11 and thus to avoid therisk of polarity reversal. The terminals B+, B− are in clamping contactwith the circuit board 11, which can be seen in particular in FIG. 10 .The electric motor 1 must also be correctly centred to ensure correctoperation of the reduction mechanism 40. The holding plate 6 performsall of these functions. This holding plate 6 makes it possible to pressthe electric motor 1 against the base of the recess 21. The holdingplate 6 is made of metal, preferably a metal which makes a springfunction possible. The holding plate 6 is fixed to the housing 20 by wayof fixing means 7, in particular screws. The housing 20 comprises a rib48 in the form of a circular arc made for the purpose of centring theholding plate 6 with respect to the housing 20, the holding plate 6having a substantially complementary shape to the rib 48. The holdingplate 6 also comprises a curved tab 49 in order to index the holdingplate 6 and the electric motor 1, the curved tab 49 being directedtowards the electric motor 1.

FIG. 8 shows the guidance of the shaft 45 in greater detail. Because ofthe high forces and torques for controlling the changing of the gearratios of the transmission, the guidance of the shaft 45 must be robust.To that end, the shaft 45 is guided in rotation by a rolling bearing 36and a bearing 51, this making it possible to absorb radial loads. Therolling bearing 36 is a ball bearing and the bearing 51 is a slidebearing.

The guide means 32 is a through-hole and has three bores of differentdiameters in which the rolling bearing 36, the bearing 51 and a lip seal52 are mounted.

The rolling bearing 36 is mounted in a first bore in order to guide theshaft 45 of the toothed-sector pinion 46 and the pin 8 mounted on theconnecting rod 9 in rotation. The rolling bearing 36 is preferablyleaktight in order not to let impurities into the internal volumedefined by the housing 20 and the cover 30. The inner race of the ballbearing 36 is mounted on the shaft 45 and the outer race is received ina first bore in the guide means 32.

The inner wall of the bearing 51 is in contact with the shaft 45 and theouter wall is in contact with a second bore in the guide means 32. Thebearing 51 is for example an antifriction slide bearing made of ametal-polymer composite. As a variant, the slide bearing may be made ofbronze.

The rolling bearing 36 is located on the outer side of the cover 30 andthe bearing 51 is located on the inner side of the cover 30.

Axially along the axis X3, a lip seal 52 is positioned in a third borein the guide means 32 between the ball bearing 36 and the bearing 51.This lip seal 52 makes it possible to make the interior of the actuatorleaktight. This is because the actuator 10 is mounted directly on thegearbox of the vehicle, and therefore the pin 8, the connecting rod 9and the ball bearing 36 are in direct contact with the lubricant of thegearbox. The ball bearing 36 is thus constantly lubricated by thelubricant of the gearbox. In other words, the lip seal 52 makes itpossible to separate a damp space, specifically the interior of thegearbox of the vehicle, from a dry space, specifically the interior ofthe actuator 10. The lip seal 52 is received in a shoulder of the guidemeans 32. The lip of the seal 52 is in contact with the shaft 45. Thelip seal 52 is in contact with one end of the bearing 51.

FIGS. 9 a and 9 b show in detail the electric connector 27 for supplyingpower to the electric motors 1 and all of the electric componentsnecessary for the operation of the actuator 10. On the side outside thehousing 20, the electric connector 27 comprises electrical tracks ableto be attached to an external connector. On the side inside the housing20, the electric connector comprises means for connection to the circuitboard 11. The electric connector 27 is made entirely of plastic and ismounted in an opening in the housing 20. The electric connector 27comprises a membrane 53, more specifically a semipermeable membrane,that is to say that it is permeable to gases, in particular air, andimpermeable to liquids, in particular water. The membrane 53 ishydrophobic and, if appropriate, oleophobic, and may have a microporouscoating. The membrane 53 may be fixed by various means to the electricconnector 27, such as by way of a ring clipped to the electric connector27. As an alternative, the membrane 53 may be adhesively bonded orsoldered to the electric connector. Such a membrane thus makes itpossible to limit the risks of condensation and overpressure within theactuator 10, and thus increases the service life whilst still improvingthe operation of the actuator.

A seal 54, which is visible in FIG. 9 b , of the O-ring type ispositioned between the electric connector 27 and the housing 20 in orderto ensure leaktightness of the actuator. The seal 54 is accommodated inan annular groove of the electric connector 27. The electric connector27 is screwed or clipped to the housing 20.

FIG. 10 shows the actuator 10 in a position mounted on the gearbox BV ofthe vehicle. The leaktightness between the gearbox BV and the actuator10 is realized by the seal 34 mounted in a groove 33 of the actuator 10,more specifically of the cover 30. The seal 34 is preferably a polymerseal. The use of a polymer seal 34 is preferred to the use of a flatmetal joint as is customary in the field.

FIG. 11 shows a variant embodiment of the actuator 10. The differencefrom the preceding embodiment is that the pin 80 is spherical and notconical. This allows adaptation to a wider variety of movable members ofmotor vehicle transmissions.

FIGS. 12 to 15 show two other variant embodiments of the actuator 10.Visible in FIGS. 12 and 13 is an actuator 200 in which there is only asingle electric motor associated with a pin 8 via a reduction mechanism.Visible in FIGS. 14 and 15 is an actuator 300 in which there are twoelectric motors associated with two pins 8 via two reduction mechanisms.The operation of the actuators 200, 300 is similar to the operation ofthe actuator 10; only the numbers of electric motors, reductionmechanisms and pins differ between the embodiments.

Such an electric actuator 10, 100, 200, 300 has a compact structure andlittle bulk. Furthermore, it is possible to use numerous standard andcommercially available elements, such as electric motors and gearwheels. The cost of such an electric actuator is furthermore relativelylow and can easily be incorporated into existing transmission systems.

Although the invention has been described in connection with a pluralityof embodiments, it is quite obvious that it is in no way limited theretoand that it comprises all the technical equivalents of the meansdescribed and combinations thereof where these fall within the scope ofthe invention.

In the claims, any reference sign between parentheses should not beinterpreted as limiting the claim.

The invention claimed is:
 1. An actuator for the actuation of at leastone movable member of a motor vehicle transmission, said actuatorcomprising: a housing; at least one electric motor having a stator and arotor mounted on a rotor shaft extending along an axis X1; a motorpinion fixed to the opposite end of the shaft from the rotor shaft; acircuit board for supplying power to the stator and controlling theelectric motor; and a reduction mechanism driven by the motor pinion andmounted on a reduction mechanism shaft, a pin configured to be engagedin the movable member of the transmission and mounted on a shaft,wherein said housing defines a first volume in which the electric motorand the circuit board are received, the circuit board is located axiallyalong the axis X1 between the electric motor and the motor pinion, andwherein the actuator further includes a cover defining a second volumein which the reduction mechanism is received, wherein the housing andthe cover each have guide means for guiding the reduction mechanism inthe form of a blind hole each respectively accommodating one end of thereduction mechanism shaft, and wherein the cover includes a through-holefor the passage and guidance of the pin shaft.
 2. The actuator accordingto claim 1, wherein the housing has at least one guide means for guidingthe reduction mechanism also serving as means for centering the circuitboard in the housing.
 3. The actuator according to claim 2, wherein thecircuit board has at least one opening of closed contour through whichthe rotor shaft of the electric motor passes and at least one opening ofclosed contour through which the guide means passes, the circuit boardbearing against a shoulder of the guide means.
 4. The actuator accordingto claim 2, wherein the outer contour of the circuit board substantiallyclosely follows the inner contour of the housing and in that the circuitboard is fixed to the housing by way of fixing means.
 5. The actuatoraccording to claim 2, wherein at least one holding plate is arranged soas to hold the electric motor in the housing, the holding plate is fixedto the housing by way of fixing means.
 6. The actuator according toclaim 2, wherein the housing comprises a peripheral groove in which aseal is disposed in order to ensure leaktightness between the housingand the cover.
 7. The actuator according to claim 2, wherein it is ableto be fixed directly on the transmission of the vehicle and in that theouter surface of the cover has a groove in which a seal is positioned inorder to ensure leaktightness between the transmission and the cover ofthe actuator.
 8. The actuator according to claim 2, wherein it comprisesat least one pin that is able to be engaged in the movable member of thetransmission.
 9. The actuator according to claim 1, wherein the outercontour of the circuit board substantially closely follows the innercontour of the housing and in that the circuit board is fixed to thehousing by way of fixing means, in particular screws.
 10. The actuatoraccording to claim 1, wherein at least one holding plate is arranged soas to hold the electric motor in the housing, the holding plate is fixedto the housing by way of fixing means.
 11. The actuator according toclaim 1, wherein the housing comprises a peripheral groove in which aseal is disposed in order to ensure leaktightness between the housingand the cover.
 12. The actuator according to claim 1, wherein it is ableto be fixed directly on the transmission of the vehicle and in that theouter surface of the cover has a groove in which a seal is positioned inorder to ensure leaktightness between the transmission and the cover ofthe actuator.
 13. The actuator according to claim 1, wherein itcomprises at least one pin that is able to be engaged in the movablemember of the transmission.
 14. The actuator according to claim 13,wherein the reduction mechanism comprises at least one gear wheelmounted on at least one reduction mechanism shaft and is locatedkinematically between the motor pinion and the pin.
 15. The actuatoraccording to claim 14, wherein the reduction mechanism comprises astepped-pinion wheel and a toothed-sector pinion.
 16. The actuatoraccording to claim 15, wherein the stepped-pinion wheel and thetoothed-sector pinion each extend in a plane orthogonal to the axis X1.17. The actuator according to claim 15, wherein the stepped-pinion wheelcomprises a first pinion and a second pinion, the first pinion iscoupled to the motor pinion and the second pinion is coupled to thetoothed-sector pinion, the stepped-pinion wheel is mounted on thereduction mechanism shaft extending along an axis X2 offset radiallywith respect to the axis X1 of the rotor shaft of the electric motor.18. The actuator according to claim 17, wherein the toothed sector ofthe pinion extends in an angular range of between 90° and 180°, thetoothed-sector pinion is mounted on a toothed-sector pinion shaftextending along an axis X3 offset radially with respect to the axes X1and the axis X2.
 19. The actuator according to claim 18, wherein the pinis mounted offset along an axis X4 at one end of the shaft of thetoothed-sector pinion by way of a connecting rod.
 20. The actuatoraccording to claim 1, wherein it is configured to change gear ratios ofa motor vehicle transmission.